In the artificial replacement of a knee joint, the impaired joint surfaces are removed and replaced by two implants that are independent of one another on the tibial and femoral side, that is to say on the upper end of the shin bone (tibia) and on the lower end of the thigh bone (femur). In that regard, the joint surface replacement on the femoral side is served by an implant that, for most known implants, consists either of a special high strength titanium alloy or of a cobalt-chromium alloy, which are cast or forged and thereafter polished. In that regard, the tibial joint side is replaced by an implant consisting of the titanium or cobalt-chrome alloy, and generally a polyethylene insert is secured thereon, which serves as the sliding tribological partner for the femoral component.
Nowadays, the artificial knee joint replacement is a reliable operation, with service lifetimes of the implants of up to 15 years. The most frequent cause of failure is the aseptic implant loosening, which is caused by abrasive wear particles of the tibial polyethylene component, and which can considerably shorten the service lifetime of an implant. The wear particles arise due to the abrasive wear of the polyethylene component, caused by the frictional abrasion with the femoral component. If the wear particles get into the bone-implant interface, biological processes are triggered on the implant-bone boundary surfaces with a cement-free anchoring or on implant-bone cement-bone boundary surfaces with a cemented anchoring, wherein these biological processes can lead to a progressive local destruction of the bone and thus finally to a loosening of the implants. If the polyethylene component of the tibia is completely consumed or used up, as a result it can additionally cause an abrasive wear of the metallic tibia plateau located thereunder, and thus allergic reactions to the metal ions that are thereby released.
Besides the metallic knee endoprostheses, a zirconium-niobium alloy is utilized under the trade name Oxinium®, of which the femoral component is transformed into a zirconium oxide ceramic in a heat treatment process at approximately 500° C., which, so to speak, represents a coating of zirconium dioxide. Furthermore, implants have become known, in which a femoral component of a mixed ceramic (BioloxDelta®) is utilized. The abrasive wear of the polyethylene is reduced by the use of this femoral component which is available in the market, in comparison to metal/polyethylene sliding tribological pairings, and in this manner the durability of the knee endoprosthesis is lengthened. However, the high manufacturing costs of the Oxinium components as well as the brittleness and the inadequate adhesion of the ceramic components on the bone cement or on the bone are to be regarded as disadvantages of these known components.
Beside these known implants, an implant of the above mentioned type in the form of a knee endoprosthesis of a metallic material has also become known from the DE 10 2011 015 300 A1, in which the sliding tribological surfaces of the femoral component already consist of a ceramic material, and in which the connection or joint between the inserts and the metallic base body of the femoral component is produced via a silicate glass solder.